Various epidemiological studies have shown an aetiological link between vitamin D deficiency and cancer incidence. The active metabolite of vitamin D, 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], has potent anti-cancer activities both in vitro and in vivo. These anti-cancer effects are attained by regulating the transcription of numerous genes that are involved in different pathways to reduce tumorigenesis and are dependent on the cancer cell type. Besides reducing cell growth and inducing apoptosis, 1,25(OH)(2)D(3) also inhibits angiogenesis and metastasis. Moreover, its potency to inhibit inflammation also contributes to its anti-tumoral activity. Here, we report the different ways in which 1,25(OH)(2)D(3) interferes with the malignant processes that are activated in cancer cells.